Expandable coil stent

ABSTRACT

An implantable coil stent comprises at least a first curved segment and a curved segment which arc about the longitudinal axis of the stent. An expandable link extends between the second end of the first curved segment and the first end the second curved segment.

BACKGROUND OF INVENTION

The use of stents to maintain the patency of bodily lumens is wellknown. are typically delivered via a catheter in an unexpandedconfiguration to a desired bodily location. Once at the desired bodilylocation, the stent is expanded and implanted in the bodily lumen. Thestent may self-expand or may be mechanically expanded. Where aself-expanding stent is used, the stent is typically retained on thecatheter via a retention device such as a sheath. The stent may bedeployed by retracting the sheath from over the stent. Where amechanically expandable stent used, a radially outward force istypically applied to the stent to expand it. The may be applied via anexpandable member such as a balloon or via any other mechanical device.

Stents are used in an array of bodily vessels including the coronaryarteries, the peripheral arteries, arteries of the neck, cerebralarteries, veins, biliary ducts, urethras, ureters, fallopian tubes,bronchial tubes, the trachea, the esophagus and the prostate.

Currently available stents include tubular stents such as the NIR™ stentas well as coil stents. Tubular stents are typically formed from tubesor from sheets of material from which material has been removed to formopenings.

Coil stents typically are formed of a wire or strand which has beenwound into coil shape. Coil stents can exhibit a high degree offlexibility, including bendability and longitudinal flexibility whichfacilitates delivery of the stent through tortuous bodily vessels.Accurate sizing of coil stents, however, can be quite challenging.

There remains a need for coil stents which are flexible and which can beeasily and accurately sized to the vessels in which they are implanted.

All U.S. patents and applications and all other published documentsmentioned anywhere in this application are incorporated herein byreference in their entirety.

Without limiting the scope of the invention a brief summary of theclaimed embodiments of the invention is set forth below. Additionaldetails of the summarized embodiments of the invention and/or additionalembodiments of the invention may be found in the Detailed Description ofthe Invention below.

A brief abstract of the technical disclosure in the specification isprovided as only for the purposes of complying with 37 C.F.R. 1.72. Theabstract is not to be used for interpreting the scope of the claims.

SUMMARY OF INVENTION

In one embodiment, the invention is directed to an implantable coilstent comprising a first curved segment and a second curved segment andan link extending between the first and second curved segments. Thefirst and second curved segments arc about the longitudinal axis of thestent. Desirably, the expandable link has at least one bend therein.

Where the stent comprises a plurality of expandable links including afirst expandable link and a second expandable link, desirably the secondexpandable is spaced along the stent from the first expandable link byat least 90 degrees and more desirably, by at least 180 degrees.

Desirably, the expandable segment is made of a first material and thecurved segment of a second material. The first material may be stainlesssteel and the second material may be nitinol. Other combinations arealso within the scope of invention. Optionally, the curved segments arein the form of one or more wires having an outer layer of material and aradiopaque core.

The invention is also directed to a coil stent comprising a firstsegment which curves about the longitudinal axis of the stent, a thirdsegment which curves about the longitudinal axis of the stent and asecond segment disposed between the first and third segments where thefirst and third segments are formed of a first and the second segment isformed of a second material different from the first material. Thefirst, second and third segments are joined end-to-end. Desirably,second segment has at least one bend therein. The second segment mayhave a plurality of bends therein.

The first material desirably is a shape memory material and the seconddesirably is stainless steel. The first material may be adhesivelyjoined to the material or joined via any other suitable technique.

The invention is further directed to a medical coil implant forimplantation in a bodily vessel. The implant comprises a strand having aplurality of winding which wind about the longitudinal axis of theimplant and a plurality of linking segments, the linking segmentsextending between winding segments which are adjacent one another alongthe coil. Each linking segment has at least one bend. Desirably, thelinking segments are made of a first material and the winding segmentsare made of a second material different from the first material. Windingsegments which are adjacent to linking segments may be adhesively bondedsoldered thereto or joined by any other suitable techniques.

It is also within the scope of the invention for the linking segmentsand the winding segments to be made from the same material, the linkingsegments been subjected to a different treatment than the windingsegments. The linking segments and the winding segments may optionallybe made of a shape memory material, for example nitinol. The shapememory material in the linking segments may be subjected to a differentheat treatment or annealing than the shape material in the windingsegments. The medical coil implant may be provided in the form of astent, vena cava filter or vaso-occlusive device.

The invention is also directed to any of the inventive medical devicesdisclosed herein in combination with a medical balloon, where themedical device is disposed about the medical balloon.

The invention is further directed to methods of deploying any of theinventive medical devices disclosed herein at a desired bodily location.In accordance with embodiment of the invention, a medical devicedelivery catheter comprising any of the inventive medical devicesdisclosed herein is provided. The catheter is in a bodily vessel to adesired location in the body and the inventive medical device caused toexpand to a first size. The expandable links are then expanded to expandthe medical device to a second size. The expansion of the expandablelinks may be accomplished by inflating a medical balloon or expandingany other mechanical expansion device disposed within the inventivemedical device or via other suitable method.

Additional details and/or embodiments of the invention are discussedbelow.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1a is a side view of a coil stent in accordance with the invention.

FIG. 1b shows an enlarged view of portion 1 b of the coil stent of FIG.1a.

FIG. 2 is a side view of a coil stent in accordance with the invention.

FIG. 3 is a side view of a vena cava filter in accordance with theinvention.

FIG. 4 is a side view of a catheter with an inventive stent disposedthereabout with parts cut away.

FIG. 5 is a side view of an inventive stent disposed about a ballooncatheter in a bodily vessel.

FIG. 6 is a side view of an inventive stent seated in a vessel.

DETAILED DESCRIPTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific preferred embodiments of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiments illustrated.

For the purposes of this disclosure, unless otherwise indicated,identical reference numerals used in different figures refer to the samecomponent.

With reference to FIG. 1a, the invention is directed, in one embodiment,to an implantable coil stent such as that shown generally at 100 in FIG.1a. Coil stent 100 is shown in FIG. 1a as it is being deployed fromcatheter 150. Coil stent 100 has a proximal end 104, a distal end 108and a longitudinal axis 112 therethrough. Coil stent 100 comprises firstcurved segment 114 a and second curved segment 114 b. First curvedsegment 114 a and second curved segment 114 b arc about axis 112 ofstent 100. First curved segment 114 a and second curved segment have afirst end 118 and a second end 120. Stent 100 further comprises link 122extending between second end 120 of first curved segment 114 a and firstend 118 of second curved segment 114 b. As shown in FIG. 1, expandablelink 122 has a plurality of bends 124 therein. The inventioncontemplates embodiments in which the expandable segment has a singlebend and embodiments in which the expandable sections has a serpentineor other bent appearance.

Desirably, as shown in the expanded view of FIG. 1b, the curvature ofexpandable links 122 at each end 122 a and 122 b is substantiallysimilar to the curvature of the ends of the curved segments 114 to avoidan excess concentration of stress at junctions between the expandablelinks and the curved segments.

The coil stent of FIG. 1a comprises a plurality of expandable links 122.nearest neighboring expandable links along the stent are spaced by atleast 90 degrees about the longitudinal axis of the stent and moredesirably, as shown in 1 a, by at least 180 degrees about thelongitudinal axis of the stent.

Coil stents comprising a single expandable link are also within thescope of the invention and any of the embodiment disclosed herein may beprovided with a expandable link.

The invention also contemplates other forms for the expandable link. Forexample, as shown in FIG. 2, expandable link 122 comprises at least onecell 126 and desirably, a plurality of expandable cells 126. Cells 126are diamond shaped. Cells of any other suitable, expandable shape may beused as well. For example, the cells may rectangular or may be definedby a curved shape.

Desirably, as shown in FIG. 2, at least one expandable link is providedper one complete turn of the stent about the longitudinal axis. Moredesirably, between and four expandable links are provided per turn ofthe stent. Stated otherwise, nearest neighboring expandable links alongthe stent desirably are spaced by between about 90 degrees and 360degrees apart about the longitudinal axis of stent. In other embodimentsof the invention, the stents may have more than four expandable linksper turn or less than one expandable link per turn of the stent. anexample of the latter, one expandable link may be provided for every twoturns the stent about the longitudinal axis of the stent.

It is also within the scope of the invention to provide a coil stenthaving at least one expandable link similar to that disclosed inconjunction with FIG. 1a and at one expandable link similar to thatdisclosed in conjunction with FIG. 2.

In one embodiment of the invention, the expandable links may be made ofstainless steel and the curved segments made of a shape memory material.shape memory materials include shape memory metals such as nitinol. Moregenerally, the expandable links may be made of a first material and thecurved segments made of a second material different from the firstmaterial. The expandable links and the curved segments may be joinedend-to-end adhesively, soldering, welding, laser welding, the use ofplasma techniques, the use of electron beams or via any other suitabletechnique. Suitable adhesives include and epoxies. Desirably, thecurvature of the ends of the expandable links will be substantiallysimilar to the curvature of the ends of the curved segments to avoidexcess concentration of stress at junctions between the expandable linksand the curved segments.

The invention is also directed to a coil stent, such as that shown at100 in FIG. 1a, comprising three segments. The three segments include:first curved segment 114 a which curves about longitudinal axis 112 ofthe stent, second curved segment 114 b which curves about thelongitudinal axis of the stent and expandable link 122 disposed betweenfirst curved segment 114 a and second curved segment 114 b where firstcurved segments and second curved segments are formed of a firstmaterial and expandable links are formed of a second material differentthan the first material or differently treated than the first material.The three segments are joined end-to-end. Desirably, as shown in FIG.1a, expandable link 122 has at least one bend therein. Optionally,expandable link 122 may have a plurality of bends therein.

Desirably, the first material is a shape memory material and the secondis stainless steel. The shape memory material may be metal or polymeric.An example of a suitable shape memory material is nitinol. Othersuitable metals for use in the inventive stents disclosed herein includeL605, MP35N and other metals having a composition of Co 45%-55% byweight, Cr 15%-25% by weight, W 12%-18.0% by weight, Ni 8%-12% byweight, Fe 1%-3% by weight and Mn 1%-2% by weight. L605 has a highmodulus of elasticity and is sufficiently radiopaque to it to be seenunder fluoroscopy. L605 is also MRI (magnetic resonance imaging)compatible. It is noted that L605 may be used in the manufacture ofstents of any other known stent designs as well including coil cells andstents comprising a plurality of interconnected bands. L605 maydesirably be employed as the second material. The second material mayalso be a polymeric material. Another suitable second material isnitinol whose superelastic properties have been destroyed.

The first material and second materials may be adhesively joined, joinedvia soldering, welding, laser welding or any of the other techniquesdisclosed herein or via any other suitable technique.

The invention is also directed to a medical coil implant, such as thatshown at 100 in FIG. 1a, for implantation in a bodily vessel. Theimplant comprises a strand having a plurality of winding segments 114a,b which wind about the longitudinal axis of the implant and aplurality of linking segments 122. Linking segments 122 extend betweenwinding segments 114 a,b which are adjacent one another with linkingsegment 122 having at least one bend.

In one embodiment, the linking segments are made of a first material andthe winding segments are made of a second material different from thefirst material. For example, the winding segments may be made of a shapememory material, for example, nitinol and the second material may bemade of stainless steel. Adjacent winding and linking segments may befused one to the other, for example by soldering, or adhesively bondedone to the other or joined together via any of the other modalitiesdiscussed in this disclosure.

In another embodiment of the invention, the linking segments (orexpandable segments) and the winding segments are made from the samematerial where the linking segments (or expandable segments) have beensubjected to a different treatment than the winding segments. Forexample, the linking segments (or expandable segments) may have beendifferently annealed than the winding segments, differently heat treatedor subject to a different chemical treatment. The implant may be madefrom a shape memory material where the shape memory of the linkingsegments (or expandable segments) has been destroyed by being to adifferent treatment than the winding segments. Heat treatment typicalfor superelastic material such as nitinol occurs in the range of 500° C.By heating nitinol based linking segments to temperatures substantiallyin excess of 500° C. and just below the melting point of about 1300° C.,the superelastic properties of the linking material will be destroyed.Such a treatment may be accomplished by first heat treating the entiretyof the shape memory material to set the shape of the coil and then byselectively heat treating the linking members to destroy thesuperelastic properties of the linking members.

Desirably, the curvature of the ends of the linking segments will besimilar to the curvature of the ends of the winding segments to avoid anexcess concentration of stress at junctions between the linking segmentsand the winding segments.

Where the stent comprises individual segments which are joined together,and the various segments are subject to different treatments, heat,chemical or otherwise, the shape of the individual segments may be setprior to, during or subsequent to joining the segments together.

Similarly, where the stent is formed from a continuous strand or stripof material, segments of which are subjected to different treatments,the shape of the stent may be established prior to, during or subsequentto the treatment of the material.

The inventive implant may be made in the form of a stent as shown inFIGS. 1 and 2, in the form of a vena cava filter, shown generally at 200in FIG. 3 or in the form of a vaso-occlusive device. To that end, any ofthe coil based vaso-occlusive devices disclosed in U.S. Pat. No.6,165,178 may be provided with expandable segments as disclosed herein.

Vena cava filters and vaso-occlusive devices may also be provided withan expandable link in the form of one or more cells such as thosediscussed in conjunction with FIG. 2 above.

Desirably, the expandable links or linking segments of any of themedical devices disclosed herein will be constructed to allow for up toa 100% additional radial expansion or more of the medical devicefollowing initial expansion of the medical device to the maximumdiameter attainable by expansion of the curved segments. The extent ofthe additional expansion provided by the expandable or linking segmentswill depend on the choice of materials and the design of the expandablelinks or linking segments. For example, where the expandable link orlinking segment comprises a plurality of bends, the extent of theadditional expansion provided by the expandable link or linking segmentwill depend on the total length of the expandable link or linkingsegment when it is unbent and on the extent to which the expandable linkor linking segment unbends during expansion.

Any of the inventive stents disclosed herein may be constructed andarranged that at least a portion of the stent tapers when the stent isin the expanded state. The stent may taper from one end to the other endor a portion of the stent may have a taper and the remainder of thestent be of constant diameter in the state. The stent may include one ormore portions of increasing diameter which are followed by one or moreportions of decreasing diameter in the expanded state.

The inventive stents disclosed herein may be constructed of any size andbe of any diameter suitable for use in a bodily vessel. Desirably, theinventive stents will range in length from about 6 mm to about 100 mm.Also desirably, the inventive stents will, in the expanded state, rangein diameter from about 1.5 mm to about mm. The expandable links willdesirably allow up to a doubling or more of the diameter of the stentbeyond the maximum diameter attainable by expansion of curved segmentsof the stent.

As discussed above, in any of the inventive medical devices (e.g.stents, grafts, vena cava filters, vaso-occlusive devices and other coilbased medical devices) disclosed herein, at junctions where segments ofdifferent material are joined together, or junctions where adjacentsegments are differently treated, the of the adjacent ends of theadjacent segments will desirably be substantially to one another toavoid an excess concentration of stress at the junctions between theexpandable links and the curved segments.

The inventive medical devices disclosed herein in various of theembodiments may be entirely mechanically expandable, for example via theuse of a medical balloon, or may be partially self-expanding. Theself-expanding mechanism may achieved through the use of a suitablytreated shape memory material for the or winding segments or through theuse of a resilient or spring-like material for curved or windingsegments. In other embodiments of the invention, the inventive medicaldevices may be entirely mechanically expandable.

The invention is also directed to grafts where the inventive stentsdisclosed herein serve as the framework. Any suitable graft materialsmay be used including collagen, polyethylene terephthalate (PET),polyethylene, polypropylene, polytetrafluoroethylene (PTFE), expandedpolytetrafluoroethylene and any other suitable polymeric material. Metalfoils may also be disposed about the stent framework.

It is noted, for the purposes of this disclosure, that the term “bend”does not refer to a specific method of construction. For example, theexpandable links and more specifically the bent segments may be formedby laser cutting or chemically etching a curved pattern in a material.The expandable links may also be formed by physically bending a wire orother piece of material.

The inventive medical devices may include suitable radiopaque coatings.For example, the inventive medical devices may be coated with gold orother noble metals or sputtered with tantalum or other metals. Theinventive medical devices may also be made directly from a radiopaquematerial to obviate the need for a radiopaque coating or may be made ofa material having a radiopaque inner core. For example, the inventivemedical devices may be made of nitinol disposed about platinum core.Such a construction is disclosed in U.S. Pat. No. 6,165,178. Any of theother coil materials and constructions disclosed in U.S. Pat. No.6,165,178 for coils may also be employed in the inventive medicaldevices disclosed herein. Other radiopaque which may be used includeplatinum, platinum-tungsten, palladium, platinum-iridium, rhodium,tantalum, or alloys or composites of these metals.

The inventive medical devices may also be provided with variousbio-coatings to enhance various properties of the inventive medicaldevices. For example, the inventive medical devices may be provided withlubricious coatings or other polymeric coatings. The inventive medicaldevices may also be provided with drug-containing coatings which releasedrugs over time. An example of a suitable polymeric coating is PTFE.

The inventive medical devices may also be provided with a sugar or moregenerally a carbohydrate and/or a gelatin to maintain the inventivemedical devices on a balloon during delivery of the medical device to adesired bodily location. suitable compounds for treating the inventivemedical devices include polymers and polymers which are dissolvable inbodily fluids. Portions of the and/or exterior of the inventive medicaldevices may be coated or impregnated the compound. Mechanical retentiondevices may also be used to maintain the inventive medical devices onthe balloon during delivery.

The inventive stents may find use in the coronary arteries, theperipheral arteries, arteries of the neck and the cerebral arteries. Thestents of the present invention, however, are not limited to use in thevascular system and may also be advantageously employed in other bodystructures, including but not limited to arteries, veins, biliary ducts,urethras, fallopian tubes, bronchial tubes, the trachea, the esophagusand the prostate. The inventive stents may be used interarterially inthe brain, deployed across the neck of an aneurysm as well as inocclusions in vessels.

The invention is also directed to a method of implanting a stentcomprising the steps of providing a stent delivery catheter, thecatheter comprising a coil stent in accordance with the presentinvention, advancing the catheter in a bodily vessel to desired locationin the body and deploying the stent at the desired bodily location. Thecatheter may then be withdrawn.

Where the stent has self-expanding characteristics, the stent may beheld in place on the catheter via a restraint such as a sheath. Thesheath may then be retracted to deploy the stent. An additional forcemay be applied to the stent via an expandable device such as a balloonin order to complete the deployment of the stent. The balloon may beused to apply a force to the stent and thereby expand expandablelink(s).

In accordance with the inventive method, a stent delivery catheter suchas that shown generally at 150 in FIG. 4. Catheter 150 includes amanifold 151 at the proximal end and an inner tube 152 which terminatesin a tip 154 at the distal end. Stent 100 is disposed about the distalend of inner tube 152. Stent 100 may be any of the inventive stentsdisclosed herein. Retractable sheath 156 covers stent 100. Pull collar160 is attached to retractable sheath 156. Pull wire 158 extends fromcollar 160 to the proximal end of the catheter.

The distal end of catheter 100 is inserted in a bodily vessel andadvanced to a desired location in the body. Retractable sheath 156 isretracted by pulling proximally on pull wire 158. As retractable sheath156 is retracted, stent 100 expands and is deployed. Catheter 150 may bewithdrawn and, as shown in FIG. 5, balloon catheter 160 advanced andpositioned with deployed stent 100. Stent 100FIG. 5 is not fullyexpanded. Balloon catheter 160 is then inflated thereby the expandablelinks and seating the stent in the desired location in bodily vessel162. The balloon catheter is then withdrawn. The seated stent is shownschematically in FIG. 6. Desirably, the expandable links will beconstructed and arranged to allow for up to 100% additional radialexpansion of the stent.

It is also within the scope of the invention to use a stent deliverycatheter includes a balloon so that the stent may be seated without theneed to withdraw stent delivery catheter and insert a balloon catheter.The catheter of FIG. 4 may be modified by including a balloon disposedbetween the stent and the inner tube and including an inflation lumen influid communication with the balloon.

The inventive stents may also be delivered through a microcatheter andpost inflated with a medical balloon.

More generally, the invention is further directed to methods ofdeploying any the inventive medical device at a desired bodily location.In accordance with one embodiment of the invention, a medical devicedelivery catheter, comprising any of the inventive medical devicesdisclosed herein is provided. The catheter is in a bodily vessel to adesired location in the body and the inventive medical device caused toexpand to a first size. The expandable links are then expanded to expandthe inventive medical device to a second size. The expansion of theexpandable links may be accomplished by inflating a medical balloon orexpanding any other mechanical expansion device disposed within theinventive medical or via any other suitable method. In accordance withthe invention, the inventive medical devices may also be deliveredthrough a microcatheter and post inflated with a medical balloon.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the claims where the term“comprising” means “including, but not limited to”. Those familiar withthe art may recognize other equivalents to the specific embodimentsdescribed herein which equivalents are also intended to be encompassedby the claims.

Further, the particular features presented in the dependent claims canbe combined with each other in other manners within the scope of theinvention such that the invention should be recognized as alsospecifically directed to other embodiments having any other possiblecombination of the features of the dependent claims. For instance, forpurposes of claim publication, any dependent claim which follows shouldbe taken as alternatively written in a multiple form from all priorclaims which possess all antecedents referenced in such dependent claimif such multiple dependent format is an accepted format withinjurisdiction (e.g. each claim depending directly from claim 1 should bealternatively taken as depending from all previous claims). Injurisdictions where multiple dependent claim formats are restricted, thefollowing dependent claims should be also taken as alternatively writtenin each singly dependent claim format which creates a dependency from aprior antecedent-possessing claim other than the specific claim listedin such dependent claim below (e.g. claim 3 may be taken asalternatively dependent from claim 1; claim 4 may be taken asalternatively dependent on claim 1, or on claim 2; etc.).

The disclosure is intended to be illustrative and not exhaustive. Thiswill suggest many variations and alternatives to one of ordinary skillin this art. All these alternatives and variations are intended to beincluded within the scope of attached claims. Those familiar with theart may recognize other equivalents to the specific embodimentsdescribed herein which equivalents are also intended to be encompassedby the claims attached hereto.

What is claimed is:
 1. A coil stent comprising a first curved segmentand a second curved segment, the first and second curved segments arcingabout the longitudinal axis of the stent, each of the first and secondcurved segments having a first end and a second end, the stent furthercomprising an expandable link extending between the second end of thefirst curved segment and the first end of the second curved segment,wherein the curved segments are made of shape memory alloys or shapememory polymers and the expandable link is made of a different materialthan that of the curved segments.
 2. The coil stent of claim 1 whereinthe expandable link has at least one bend therein.
 3. The coil stent ofclaim 2 comprising a plurality of expandable links, each link having atleast one bend therein.
 4. The coil stent of claim 3 wherein theplurality of expandable links includes first expandable link and asecond expandable link, the second expandable link spaced along thestent from the first expandable link by at least 90 degrees.
 5. The coilstent of claim 3 wherein the plurality of expandable links includesfirst expandable link and a second expandable link, the secondexpandable link spaced along the stent from the first expandable link byat least 180 degrees.
 6. The coil stent of claim 1 wherein theexpandable segment is made of stainless steel and the curved segmentsare made of nitinol.
 7. A coil stent comprising a first curved segmentand a second curved segment, the first and second curved segments arcingabout the longitudinal axis of the stent, each of the first and secondcurved segments having a first end and a second end, the stent furthercomprising an expandable link extending between the second end of thefirst curved segment and the first end of the second curved segment,wherein the curved segments are in the form of a wire having an outerlayer of material and a radiopaque core.
 8. In combination, the coilstent of claim 1 and a medical balloon, the coil stent disposed aboutthe medical balloon.
 9. A coil stent having a longitudinal axis, thestent comprising a first segment which curves about the longitudinalaxis of the stent, a third segment which curves about the longitudinalaxis of the stent and a second segment disposed between the first andthird segments, the first and third segments formed of a first material,the second segment formed of a second material different from the firstmaterial, the first, second and third segments joined end-to-end. 10.The coil stent of claim 9 wherein the second segment has at least onebend therein.
 11. The coil stent of claim 10 wherein the first materialis a shape memory material and the second material is stainless steel.12. The coil stent of claim 11 wherein the first material is adhesivelyjoined to the second material.
 13. The coil stent of claim 9 where thesecond segment has a plurality of bends therein.
 14. In combination, thecoil stent of claim 9 and a medical balloon, the coil stent disposedabout the medical balloon.
 15. A medical coil implant for implantationin a bodily vessel, the implant having a longitudinal axis, the implantcomprising a strand having a plurality of winding segments which windabout the longitudinal axis of the implant and a plurality of linkingsegments, the linking segments extending between winding segments whichare adjacent one another, each linking segment having at least one bendwherein the linking segments are made of a first material and thewinding segments are made of a second material different from the firstmaterial.
 16. A medical coil implant for implantation in a bodilyvessel, the implant having a longitudinal axis, the implant comprising astrand having a plurally of winding segments which wind about thelongitudinal axis of the implant and a plurality of linking segments,the linking segments extending between winding segments which areadjacent one another, each linking segment having at least one bendwherein the linking segments and the winding segments are made from thesame material, the linking segments having been subjected to a differenttreatment than the winding segments.
 17. The medical coil implant ofclaim 16 wherein the linking segments and winding segments are made of ashape memory material.
 18. The medical coil implant of claim 17 whereinthe shape memory material the linking segments has been subject to adifferent heat treatment than shape memory material in the windingsegments.
 19. The medical coil implant of claim 17 wherein the shapememory material the linking segments has been subject to a differentannealing treatment the shape memory material in the winding segments.20. The medical coil implant of claim 17 wherein the shape memorymaterial nitinol.
 21. The medical coil implant of claim 15 in the formof a stent.
 22. The medical coil implant of claim 15 in the form of avena cava filter.
 23. The medical coil implant of claim 15 whereinwinding segments which are adjacent to linking segments are adhesivelybonded thereto.
 24. The medical coil implant of claim 15 wherein windingsegments which are adjacent to linking segments are soldered thereto.25. The medical coil implant of claim 15 wherein the linking segmentsare made of L605.
 26. In combination, the coil stent of claim 15 and amedical balloon, the coil stent disposed about the medical balloon. 27.A method of deploying a stent at desired bodily location comprising thesteps of: providing a stent delivery catheter, the stent deliverycatheter comprising the coil stent of claim 1, the stent disposed aboutthe medical balloon; advancing the catheter in a bodily vessel to adesired location in the body; causing the stent to expand to a firstdiameter; and expanding the expandable links to further expand the stentto a second diameter.
 28. The method of claim 27 wherein the stent is atleast partially self-expanding.
 29. The method of claim 27 wherein thestent delivery catheter further comprises a medical balloon and thestent is disposed about the medical balloon.
 30. The method of claim 29wherein the expanding step includes inflating the medical balloon toapply an outward force to the expandable links.